Abstracts and presentations are embargoed for release at date and time of presentation or time of AHA/ASA news event. Failure to honor embargo policies (http://newsroom.heart.org/newsmedia/embargo-policy) will result in the abstract being withdrawn and barred from presentation.

Jump to

Abstract

Recently, we have shown that extracellular vesicles (EVs) produced by GATA-4-overexpressing mesenchymal stem cell (MSCs) (EVGATA-4) significantly improved ischemic myocardial function, compared to EVs from vector-empty transfected MSCs (EVnull). We hypothesized that EVGATA-4 promoted angiogenesis in ischemic myocardium via miRs released in recipient cells. MSCs were transduced with GATA-4 using the murine stem cell virus retroviral expression system and EVs were harvested from the conditioned media of MSCGATA-4 and its control counterpart MSCnull. The tubular structures formation of human umbilical vein endothelial cells (HUVECs) and Matrigel plug were used to evaluate angiogenesis. The data of MicroRNA-seq showed that 358 miRs were found in EVs, 46 were significantly increased and 64 were decreased in EVGATA-4 compared to EVnull. Of the 46 upregulated miRs, many were pro-angiogenetic and pro-survival factors; most notably, the let-7 family members. The tube formation was significantly increased in HUVECs treated with EVGATA-4 than in those treated with EVnull. The cumulative sprout length per spheroid was also greater in EVGATA-4-treated HUVECs than EVnull-treated cells. Following Matrigel containing EVs (100μg/plug) subcutaneously transplanted into mice for 2 weeks, EVGATA-4 significantly increased the blood flow compared to EVnull. Real-time imaging system recorded that EVs could be internalized by HUVECs. The expression of let-7 was significantly upregulated in HUVECs following EVGATA-4 treatment. Thrombospondin 1 (THBS1) is an anti-angiogenic gene and one of the potential target genes of let-7f. It was down-regulated in HUVEC treated with EVGATA-4 compared with that treated with EVnull. To investigate the effect of transferred let-7 on angiogenesis, EVs were collected from MSCs transfected with let-7f inhibitor (anti-let-7f) or from MSCs transfected with let-7f mimic, respectively. The tube-like structure formation following different EVs treatment was positively related to the expression of let-7f in HUVECs. These results suggested that EVGATA-4 increased angiogenesis, which is associated with the transfer of pro-angiogenetic miRs to regulate their targets in HUVECs.